Russian opposition leader Boris Nemtsov is being charged in two separate courts in connection with helping organize unsanctioned protests in Moscow.

The co-leader of the Solidarity movement was arrested on August 22, when he and around 100 other activists tried to march through the capital carrying a giant Russian flag. They were marking Flag Day, which honors the tricolor flag adopted 20 years ago by democratic Russia following the Soviet collapse.

Police also detained around 20 others, including another Solidarity member, the prominent human rights activist Lev Ponomaryov, for taking part in the unsanctioned march, although officials said the activists had permission to hold a stationary rally.

Speaking by telephone to RFE/RL's Russian Service shortly after his arrest, Nemtsov said the decision to stop the march showed the mentality of Prime Minister Vladimir Putin's government.

He called Russia's current authorities "the ideological heirs" of the 1991 coup organizers. "For them the Russian flag is a symbol of freedom, a symbol of human dignity, a symbol of democracy. They hate freedom, despise dignity, and consider democracy the biggest threat to their power," Nemtsov said.

Nemtsov is being charged with refusing to obey the police. He's being accused of the same charge later on August 24 in a second court over another unsanctioned protest in July, when he was briefly arrested.

Forest Protest

The charismatic former deputy prime minister -- who was once tapped by ex-President Boris Yeltsin to be his chosen successor -- denies both charges. He faces possible fines and prison sentences of up to 15 days in each case.

WATCH: Musicians perform at the rally without microphones or equipment, while activists in the crowd chant "Send the route around the forest!" and "Russia without Putin!"

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Nemtsov and the other marchers were on their way to another protest in central Pushkin Square on August 22, when up to 2,000 demonstrators protested the building of a highway though a protected forest in the northwestern Moscow suburb of Khimki. The turnout was higher than during other recent rallies, over an issue that's becoming a national symbol of opposition to the authorities.

City officials had rescinded earlier permission for organizers to hold a concert, and police blocked participants carrying musical instruments and sound equipment to the square. But some musicians, including veteran rocker Yury Shevchuk, nevertheless sang songs without a microphone and strummed acoustic guitars.

On August 21, 3,000 protesters attended a rally in the Baltic Sea exclave of Kaliningrad to demand Putin's resignation and a return to the direct elections of regional governors. But that protest was significantly smaller than a rally of 10,000 there last January.written by Gregory Feifer with reporting by RFE/RL's Russian Service